Eat Your Leafy Greens, Grandma!

I bet you remember as a kid being told by your parents to “eat your veggies, even the greens.” But I bet you don’t remember your parents telling THEIR parents to eat their veggies. The vast effects from eating vegetables and having a healthy diet in younger developmental stages are enumerable, but consequences of diet on elderly populations are often overlooked.

Figure 1. Vitamin K can be naturally found in several leafy green vegetables, as shown above.

What is in these magical green veggies (lettuce, kale, spinach) anyway? Amongst other things, a notable compound present is vitamin K. This vitamin is most notably used in the body to promote protective blood clotting. However, other potential roles of vitamin K in the brain have been examined in rats. Vitamin K is present in high levels in the brain, and proteins that rely on vitamin K to function are also found in the brain. These same studies found evidence for vitamin K to specifically have effects in the aging brain. Older rats that were fed a vitamin K rich diet had better spatial learning memory than those fed a low vitamin K diet. This phenomenon was only observed in older rats, not the younger populations.

The only study to date that investigated the role of vitamin K in human aging populations reported lower vitamin K levels in subjects with Alzheimer’s disease. The current study was in fact the first study to investigate the role of vitamin K in cognition in aging populations.

Healthy older adults (70-84 year olds) were extensively screened to be deemed ‘in good health’ with no cognitive impairments. They were then examined for an association between vitamin K levels and performances on a battery of cognitive tests. These cognitive tests assessed several different components of memory, as the researchers hoped to target which aspect of memory, if any, vitamin K affects.

Higher vitamin K levels were significantly associated with better performance in one type of cognitive test, but not any of the others. This test was a measure of verbal episodic memory, memory of events with their space-time context. The subjects were given a list of 16 words then asked to recall any words they remembered in three successive immediate trials. Lastly, they were given a 20-minute delay and then asked to recall the words. The significant associations between better performance and higher vitamin K levels were found for all recall trials, except for the first immediate trial. The lack of association between performance on the first immediate trial and vitamin K levels indicates that vitamin K plays no role in the process of initial memory storage. The association of better performance and higher vitamin K in the later trials shows that vitamin K plays a role in the process of stabilizing this memory trace for long-term storage, or memory consolidation. This finding was also validated in rats. These rats also showed alterations at the anatomical level in a region of the brain responsible for this process of memory consolidation, further proving this point.

Figure 2. Results demonstrating that higher vitamin K levels are associated with better performance on the 2nd, 3rd, and delayed free recall trials, but not the first.

This study proves that the role of nutrients, particularly vitamins, is complex and often misunderstood. The direct relationship between diet and memory is of great research importance because this could be used as a preventive measure for cognitive decline in elderly patients.